On May 31, 1889, a 40-foot wall of water destroyed most of the city of Johnstown, Pennsylvania. More than 2,000 people were killed, including 99 whole families and 400 children under the age of 10. Hundreds of homes and businesses were destroyed. Photographs of the city after the flood resemble images of a war zone.

The best book about the historic flood is David McCullough’s The Johnstown Flood (1968). It was McCullough’s first book, and it is still in print. The celebrated author and historian, a native of southwestern Pennsylvania, blames the disaster on nature and human indifference and callous neglect.

Nature’s contribution to the calamity came in the form of a late-spring heavy snow that melted quickly, followed by 11 straight days of rain in May, culminating in a severe storm on May 30 that dumped between 8 and 10 inches of rain on the soaked ground. The small rivers and streams that fed Lake Conemaugh swelled, causing the lake to rise to the top of the 72-foot earthen South Fork Dam.

Lake Conemaugh was created by the South Fork Fishing and Hunting Club, whose members included Andrew Carnegie, Andrew Mellon, Henry Frick, Philander Knox, and other wealthy Pittsburghers. The lake was three miles long and a mile wide at its widest point, with a capacity of more than 650 million cubic feet of water. The earthen dam, which formed and held back the lake, was around 900 feet across. Despite repeated warnings that the dam was structurally unsound, club members did little to repair or reinforce it. There had been several previous false alarms during heavy rainstorms that the dam was going to break, but each time it held back the water.

At about 3 p.m. on May 31, 1889, the dam broke. “The lake seemed to leap into the valley like a living thing,” McCullough wrote. It took about 35 to 40 minutes for the lake to empty into the valley on its 14-mile journey between the mountains to Johnstown. The tremendous wave of water and debris wiped out the towns of Mineral Point, East Conemaugh, and Woodvale, which lay directly in its path. On its way to Johnstown, the wall of water and debris stalled for a moment at a railroad viaduct. “Now, for a brief instant,” McCullough explained, “Lake Conemaugh formed again … It gathered itself together, held now by another dam, which however temporary was nonetheless as high as the first one; and when this second dam let go, it did so even more suddenly and with greater violence than the first one. The bridge collapsed all at once, and the water exploded into the valley with its maximum power now concentrated again by the momentary delay.”

At about 4 p.m., witnesses recalled hearing a thunderous roar and seeing a 40-foot wall of water and debris crash into Johnstown. When the surging water finally came to rest at a stone bridge at the southern end of the city, what remained of Johnstown was, in McCullough’s words, “a vast sea of muck and rubble and filthy water.” That evening, debris at the stone bridge caught fire, and up to 80 people burned alive. Cleanup crews were still finding dead bodies months later.

If you want to learn more about this tragic disaster, read McCullough’s book, and then visit the Johnstown Flood Memorial, which is located at the sight of the South Fork Dam and is operated by the National Park Service. After watching a short film at the visitor center, you can walk into the empty lakebed and look up at the remnants of the South Fork Dam. The South Fork Fishing and Hunting Club’s building still stands at the edge of the empty lakebed.

Then travel the 14 miles to Johnstown, where there are markers in some places showing the level reached by the floodwaters, and visit the Johnstown Flood Museum, which includes many photographs and a model of the valley through which the waters of Lake Conemaugh traveled on that fateful day. The Johnstown “incline” will take you up a hillside where you can overlook the city and see the valley opening where the destructive wall of water entered the city. Finally, and solemnly, you can visit the Grandview Cemetery, where some of the dead were buried in a mass grave named the “plot of the unknown.” Three years after the flood, a “Monument to the Unknown Dead” was erected at the cemetery that features the allegorical women Faith, Hope, and Charity. Hope points upward toward the heavens — the final destination of the flood’s victims.